Valves of the kind described above are used for blocking and opening gas or liquid conduits such as in connection with a known pipetting bulb for drawing liquid by suction in pipettes. Such pipette bulbs are sold in the Federal Republic of Germany by Rudolf Brand GmbH & Co. under product No. 253 00. The known pipetting bulbs have suction and ventilating valve bodies in the form of spherical valve bodies mounted in corresponding elastic suction and ventilating conduits. The particular conduit lies as a casing about a valve ball and sealingly closes the latter about its periphery. By partially squeezing the casing against the hard surface of the valve ball, the casing deflects in response to the pressure force and lifts off of the portion of the valve ball which is not subjected to pressure. In this way, a through-flow path is provided to allow the fluid to pass.
The known valves can only be actuated manually because the squeezing force must be applied at the periphery of the valve ball lying against the inner wall surface of the wall casing. A squeezing pressure applied ahead or behind of this periphery (large circle of the valve ball) leads only to an intensified closure of the conduit. Accordingly, the suitable location on the conduit for applying the squeezing pressure must first be found by a skilled hand and this must be preceded by feeling the wall casing with the fingers to find the correct location.
However, in many applications, it is necessary that the valves not be actuated manually since the hands must remain free for other work. An example of such an application is when the valve is within a drinking line for taking up liquid nourishment or medicine by the wearer of a protective suit and/or of a hood. This can, for example, be necessary for a pilot during a flight or for a wearer of a protective suit or of a protective mask while present in a poisonous or contaminated atmosphere.
Such an application is described in French Pat. publication No. 747,066. In the arrangement described in this publication, the valve is disposed outside of the protective mask and must be actuated manually. Damage to the hose downstream of the valve would lead to an unwanted penetration of contaminants into the enclosed space of the mask. A placement of the valve within the inner space of the mask would make its actuation impossible.